I've visited the 9/11 Memorial a couple of times so skipped it on this trip; One World Trade Center (ie Freedom Tower) is still jaw-dropping as the tallest building in the Western Hemisphere (the same architect designed Willis Tower and Burj Khalifa)
The Fairmont Copley Plaza (w/ John Hancock Tower at left) opened in 1912; Frederick Kerry, paternal grandfather of Senator John Kerry, committed suicide here in 1921; in the 1920s, John Singer Sargent kept rooms here where he painted portraits